UNIX for Dummies Questions & Answers

I have a problem. Someone gave me a 9-Track reel-to-reel tape and told me to get the information off of it. The only thing that was given to me along with it was this information:
Magnetic Tape: 6250 BPI
EBCDIC
9-Track

Record Size = 60 Bytes
Records/Block = 60


I am pretty sure that the information came from a mainframe computer and I am positive that this has been done before using the dd command.

If I use dd with the default values or obs=60 I get nothing back. Can anyone give me any ideas on how to extract the data from this tape?

If each record is 60 bytes and you have 60 records per block, then each block is 3600. If you're writing to a disk file, the obs is irrelevant. It's the ibs which is critical. Although I would just use bs=3600.

Mainframes tend to have a concept called "labelled tape". The label will appear to you as a tiny file at the beginning of the tape. If your tape is labelled, you will get only one or two short records. Use the no-rewind device and if the dd gives you a very short file, run it again and you may get the real file.

You have ebcdic and you probably want ascii, so you will need to use conv=ascii on the dd statement.

That certainly helped but now I have another problem. The data was extracted to one file. If I cat the file it looks something like this:
&M-^@^@M-^W^@^B&M-4^@1^@^@^@^@M-&M-^QM-$ M-^Q^A M-^Q^A{^@^@M-=M-2M-JSANTA MONICA
The data does not seem to be compressed because you can clearly make out certain words, however, I'm pretty sure that the file or files are all supposed to be just text. Does anyone have any ideas on how I might be able to extract this data?

Did this by any chance come from a Unisys mainframe?

I'll give you one guess where it came from and you probably know better than I do what kind of mainframe it was.

I thought so, but I wasn't sure.
I'm looking at some of our manuals here as to the tape format defaults.

I'm checking with some people here too, since they write tapes all the time. Also, a BLOCKSIZE of 60 seems a little odd - the default on LIBRARY/MAINTENANCE tapes are 2701.

And another thing would be the number and size of headers. You have Volume Headers, Header Labels, Tape Directories, all seperated by TAPEMARKS before the data ever starts.

And yet another problem could be the exact OS and version.
I don't recall if it was a OS/2200 or an MCP machine - it might not matter though.

Yet all of this could be irrelevant if they decided to use some other format than the usual.

I'll look into it some more.

What type of system are you dumping this to? Do you need to add the "conv=ascii" to the dd command or does your system use ebcdic?

(Sorry! Didn't see that Perderabo had covered that)